Bug report

Bug description:

Plotting the Faster CPython team's weekly benchmarks, there is an obvious discontinuity in the python_startup_no_site benchmark:

This is between these two commits:

2025-03-03 0.98 b3c18bf
2025-03-08 0.85 a3990df

Bisecting over this range, it's reproducible that the first bad commit isc6dd2348ca.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-132952: Improve Python startup time by ~12% #132956
• gh-132952: Import _io instead of io at startup #132957